The present invention relates to adjustable steering column mechanisms, and more particularly, to such mechanisms which permit both telescoping and tilting of the column and steering wheel.
Adjustable steering columns have become quite popular, especially for commercial vehicles, such as trucks, which the operator may drive continually over a long period of time. The ability to adjust the steering column and steering wheel greatly enhances the comfort of the driver and compensates for the varying sizes of drivers and the varying seat positions utilized by different drivers.
Prior art adjustable steering column mechanisms have generally provided either a telescopic movement of the column, providing linear movement of the steering wheel toward and away from the driver, or a tilting movement of the column, providing pivotal movement of the steering wheel about an axis perpendicular to the steering column, although a few relatively complex mechanisms have provided for both telescopic and tilting movement. Among the mechanisms which have had the capability of both telescopic and tilting adjustment, there has typically been the disadvantage that more than one movement of a handle or control member would be necessary to affect both modes of movement.
Adjustable steering column mechanisms have generally been of either the detent type or the friction type. Typically, in the detent type, a detent mechanism is operable to engage a movable member having a plurality of holes or slots, each of which corresponds to a separate, discreet position of the steering column. Another disadvantage of the detent type of mechanism is that by its very nature, the manufacturing tolerances of the mating and engaging parts must be held very close in order to avoid looseness and an undesirable, noisy rattling of the parts.
In a typical mechanism of the friction type, a pair of relatively movable members (such as an inner tube and an outer tube) have adjacent surfaces clamped together with sufficient force that the resulting frictional force maintains the members in a fixed relative position. The friction type mechanism generally has the advantage of being infinitely adjustable within the given range, but generally has the disadvantage of insufficient locking force, especially when the vehicle operator swings himself into the cab while holding onto the steering wheel.